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Key Study Findings - Emerging Applications

The following Key Study Findings are just a sample of the more than 600 compelling clinical presentations, study abstracts and published papers documenting INVOS® System benefits.

To see the full bibliography, please visit Clinical Evidence.

Noninvasive Assessment of TBI Patients




Twelve patients with traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH) were monitored with noninvasive cerebral oximetry and an invasive brain oxygen probe (tissue PO2) for a median of 26 hours each in the ICU. Over 427 hours of data (over 104,000 data points) were analyzed.
  • The investigators transformed the data mathematically to compare changes occurring in both monitors in certain frequency bands.
  • The study validated that the two devices are measuring the same thing (cerebral oxygenation).
  • The INVOS® System can provide oxygenation information to clinicians on patients suffering from TBI or SAH in a noninvasive, risk free way.

Footnote:
Brawanski, et al. Journal of Cerebral Blood Flow and Metabolism 2002;22:606-11.

Avoid Catastrophic Events during Beach Chair Procedures

The "barbershop" or "beach chair" position describes the 30-90 degree angle that a patient is positioned in during shoulder arthroscopy and other procedures. Even in young, healthy, adults, significant physiologic changes can occur in this upright position which can compromise adequate cerebral blood flow and lead to devastating outcomes.

A thorough understanding of physiologic changes associated with the upright position, and the effects of hypotension on blood pressure in the brain is crucial to prevent catastrophic neurological outcome during shoulder surgery in this sitting position.
  • Cerebral autoregulation has been thought to maintain cerebral blood flow (CBF) constant between MAP of 50-150 mmHg, but some orthopedic surgeons request deliberate hypotension for shoulder surgery.
  • Deliberate hypotension to MAP of 50-60 mmHg eliminates any margin for error in case blood pressure falls further.
    • In the upright position, the effect of venous outflow on cerebral perfusion pressure (CPP) is very different when compared to the supine position. This difference may be overlooked.
    • During prolonged periods of deliberate hypotension, neuromonitoring with the with the INVOS® System should be considered.

Footnote:
Pranevicius M et al, Anesth Patient Safety Found Newsletter. Summer 2008 32-33.

Spinal Ischemia Monitoring



Sensor placement to monitor for spinal ischemia.

This study showed that transcutaneous NIRS via the INVOS® System detects declines in oxygen saturation during intraoperative spinal cord ischemia in a porcine model.
  • Subarachnoid injection of indocyanine green dye increased NIR light absorption; indicating a portion of NIR photons penetrate tissues to the depth of the spinal cord.
  • NIRS sensors were placed on the upper (T6-T7) and lower (T9-T11) spine, followed by sequential clamping of the thoracic 6 to lumbar 1 vertebrae.
    • As blood flow to the lower spinal cord decreased, so did rSO2 values.
    • A histopathologic exam of the spinal cord found an increase in ischemic neurons that paralleled rSO2 readings.
  • Authors state "the inability to directly measure spinal cord blood flow and oxygenation intra-operative is a major obstacle to preventing paraplegia after Thoraco-Abdominal Aneurysm surgery..."Real time information about spinal cord perfusion during Thoraco-Abdominal Aneurysm would allow the surgical team to intervene when ischemia occurs."


Footnote:
LeMaire SA, et al. J Thorac Cardiovasc Surg 2006;132:1150-1155.

Cerebral Perfusion Pressure and Autoregulation




Managing cerebral perfusion pressure (CPP) in patients with traumatic brain injury (TBI), stroke, meningitis, cardiopulmonary bypass and following circulatory arrest is challenging due to limitations of monitoring capabilities. Relying on arterial blood pressure for measurement of CPP is less than ideal.
  • This animal study used laser-Doppler flowmetry to assess autoregulation in piglets, which were made progressively hypotensive.
  • Cerebral oximetry index (COx) using the INVOS® System had 92% sensitivity and 63% specificity for detecting loss of autoregulation as a result of hypotension.
  • COx correlated with laser-Doppler derived time-domain analysis of spontaneous autoregulation (LDx) when stratified by CPP, r=0.67.
  • Noninvasive, continuous NIRS monitoring with the INVOS® System could be a valuable adjunct device for actively optimizing CPP in patients with severe head injury.

Footnote:
Brady KM, et al. Stroke 2007 Oct;38(10)2818-25. Epubl 2007 Aug 30.